﻿package  {
    import flash.utils.ByteArray;
    public class Base64 {
        private static  const encodeChars:Array =    
                ['A','B','C','D','E','F','G','H',   
                'I','J','K','L','M','N','O','P',   
                'Q','R','S','T','U','V','W','X',   
                'Y','Z','a','b','c','d','e','f',   
                'g','h','i','j','k','l','m','n',   
                'o','p','q','r','s','t','u','v',   
                'w','x','y','z','0','1','2','3',   
                '4','5','6','7','8','9','+','/'];
        private static  const decodeChars:Array =    
                [-1, -1, -1, -1, -1, -1, -1, -1,   
                -1, -1, -1, -1, -1, -1, -1, -1,   
                -1, -1, -1, -1, -1, -1, -1, -1,   
                -1, -1, -1, -1, -1, -1, -1, -1,   
                -1, -1, -1, -1, -1, -1, -1, -1,   
                -1, -1, -1, 62, -1, -1, -1, 63,   
                52, 53, 54, 55, 56, 57, 58, 59,   
                60, 61, -1, -1, -1, -1, -1, -1,   
                -1,  0,  1,  2,  3,  4,  5,  6,   
                 7,  8,  9, 10, 11, 12, 13, 14,   
                15, 16, 17, 18, 19, 20, 21, 22,   
                23, 24, 25, -1, -1, -1, -1, -1,   
                -1, 26, 27, 28, 29, 30, 31, 32,   
                33, 34, 35, 36, 37, 38, 39, 40,   
                41, 42, 43, 44, 45, 46, 47, 48,   
                49, 50, 51, -1, -1, -1, -1, -1];
        public static function encode(data:ByteArray):String {
            var out:Array = [];
            var i:int = 0;
            var j:int = 0;
            var r:int = data.length % 3;
            var len:int = data.length - r;
            var c:int;
            while (i < len) {
                c = data[i++] << 16 | data[i++] << 8 | data[i++];
                out[j++] = encodeChars[c >> 18] + encodeChars[c >> 12 & 0x3f] + encodeChars[c >> 6 & 0x3f] + encodeChars[c & 0x3f];
            }
            if (r == 1) {
                c = data[i++];
                out[j++] = encodeChars[c >> 2] + encodeChars[(c & 0x03) << 4] + "==";
            } else if (r == 2) {
                c = data[i++] << 8 | data[i++];
                out[j++] = encodeChars[c >> 10] + encodeChars[c >> 4 & 0x3f] + encodeChars[(c & 0x0f) << 2] + "=";
            }
            return out.join('');
        }
        public static function decode(str:String):ByteArray {
            var c1:int;
            var c2:int;
            var c3:int;
            var c4:int;
            var i:int;
            var len:int;
            var out:ByteArray;
            len = str.length;
            i = 0;
            out = new ByteArray();
            while (i < len) {
                // c1   
                do {
                    c1 = decodeChars[str.charCodeAt(i++) & 0xff];
                } while (i < len && c1 == -1);
                if (c1 == -1) {
                    break;
                }
                // c2       
                do {
                    c2 = decodeChars[str.charCodeAt(i++) & 0xff];
                } while (i < len && c2 == -1);
                if (c2 == -1) {
                    break;
                }
                out.writeByte((c1 << 2) | ((c2 & 0x30) >> 4));
                // c3   
                do {
                    c3 = str.charCodeAt(i++) & 0xff;
                    if (c3 == 61) {
                        return out;
                    }
                    c3 = decodeChars[c3];
                } while (i < len && c3 == -1);
                if (c3 == -1) {
                    break;
                }
                out.writeByte(((c2 & 0x0f) << 4) | ((c3 & 0x3c) >> 2));
                // c4   
                do {
                    c4 = str.charCodeAt(i++) & 0xff;
                    if (c4 == 61) {
                        return out;
                    }
                    c4 = decodeChars[c4];
                } while (i < len && c4 == -1);
                if (c4 == -1) {
                    break;
                }
                out.writeByte(((c3 & 0x03) << 6) | c4);
            }
            return out;
        }
    }
}